Also, and I'm sorry for the cliche, but never underestimate the power of a strand of pearls. You can borrow them, they can be a nice faux set if need be.

Have fun!

Black belt shopper here: Jeans are not formal wear except in Hollywood. If you are talking black tie formal a black dress in a better fabric (NOT a knit) is appropriate and can be changed up to go to more than one event. For a wrap a pashmina or a fancy sweater is good. PLEASE remember that a daytime black leather bag is not your best choice as an accessory.

If this is a "formal" event like business meeting a cute dress in a more casual fabric is good. (I call this country club casual). A clutch purse as opposed to a satchel is better. You can also wear nice (wool) slacks and a fancy sweater in some places, but in general a dress is preferable.

I would love to go shopping with you. :D

^^^ ditto!

Ladies, we can shop together anytime!!! For whatever perceived faults my children and husband may find in me (fools that they may be), I do shop extraordinarily well. :)

If it was "formal dinner" at my school, that would mean pin attire, because we do formal dinner before chapter meeting. LBD and pearls would be waaaaay over dressed. Dress pants and a nice sweater would be appropriate.

Perhaps this chapter is having a formal dinner in the true sense of the word formal, and the LBD would be appropriate.

In either case, nice jeans are probably not appropriate.

Since the OP hasn't let on any other information about what "formal dinner" means to the chapter in question, she is better off PMing someone from her campus. If she goes where I think she goes, there are plenty of posters from that school. Otherwise, I don't see a problem with asking the person who sent the invitation.